1. Field of the Invention
The present invention is related to the field of the parts made out of composite materials, and more in particular the field of the parts intended for being assembled with other parts, and likely to be subjected to pulling and compression forces.
The object of the present invention is thus a method for manufacturing such a part made out of composite material to be subjected, via at least one attachment point, to pulling and compression forces, as well as the resulting part.
The present invention will find a particular application in the field of the manufacture of connecting rods, and is thus also related to a connecting rod manufactured according to the inventive method.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
It is known that the weak point of the composite materials is the thermoplastic or thermosetting matrix, in which the reinforcing fibers are embedded, and which generally consists of a resin, because it has a specific resistance much lower than that of the fibers. The way of ruining a part made out of composite material is generally a breaking of the resin connecting the fibers.
A good design of a composite part takes this phenomenon into consideration and favors a transmission of the forces through putting the fibers purely under a pulling or compression force, which results into not stressing the resin. Thus, the composite material is formed of layers of fibers oriented according to the direction of said forces or according to directions close to the latter.
This can easily be achieved at the level of the main portion of the part when the shapes are simple and the direction of the forces is under control, it is however difficult at the level of the areas of connection to one or several other parts, namely the areas in which the pulling or compression force is exerted.
Generally, such a connection area includes an insert provided with a connecting means permitting to carry out the connection and the transmission of the forces into the part, but the placing of such inserts is particular difficult, namely when the forces vary during the utilization of said composite part.
The main drawback is thus at the level of the junction of the body of the composite part with the insert, and is related to the transmission of the force between them.
In order to cope with this drawback, there has been provided, namely in FR 2 125 289, a force-transmitting organ, such as a connecting rod, made out of fiber-reinforced synthetic material. This organ comprises a tubular central body containing fibers oriented according to a direction in which the forces are exerted, and the ends of which are narrowed into a truncated shape in order to make integral with each of them a connecting means, which is formed of two parts, an internal one and an external one, so as to be capable of enclosing the narrowed portion of the tubular central body.
However, this force-transmitting organ only partially copes with the problems of connecting the body of the composite part with the insert, and problems of strength and resistance in time persist.